The present invention relates to a method of and to an apparatus for pneumatically transporting rodshaped articles, especially filter rod sections and other rod-shaped articles which constitute or form part of smoker's products. More particularly, the invention relates to improvements in methods and apparatus for transporting filter rod sections or the like from a sending station to a receiving station by way of a pneumatic conveyor. As used herein, the term "rod-shaped articles" is intended to embrace, among others, filter rod sections, plain cigarettes, cigarillos or cigars, filter cigarettes, cigarillos or cigars, cheroots and like articles wherein a tubular wrapper normally confines a mass of natural, reconstituted and/or substitute tobacco and/or filamentary, granular and/or other filter material.
It is customary to pneumatically transport rod-shaped articles of the tobacco processing industry between spaced-apart locations, e.g., from a filter rod making machine to a remote magazine which stores a supply of such articles adjacent to a filter tipping machine wherein filter rod sections are united with plain cigarettes to form filter cigarettes of unit length or multiple unit length. A sender at the sending station is designed to propel successive rod-shaped articles into the inlet of a pneumatic conveyor which can be several hundred meters long, and the outlet of the conveyor admits the articles into the magazine of the receiver. The sender can be designed to supply rod-shaped articles from a centrally located main storing or making station to two or more discrete filter tipping machines.
A sender which is presently preferred by many manufacturers of smokers' products is disclosed in commonly owned U.S. Pat. No. 3,827,757 to Heitmann et al. This sender is associated with means for transferring rod-shaped articles from a source of supply to a position of readiness for pneumatic propulsion into the inlet of the pneumatic conveyor. A receiver which can accept and temporarily store the thus propelled articles is disclosed in commonly owned U.S. Re. Pat. No. 28,383 to Rudszinat. The patented receiver is equipped with means for withdrawing successive rod-shaped articles from the pneumatic conveyor and for transferring them into the magazine.
A drawback of presently known pneumatic transporting systems for rod-shaped articles is that the admission of articles into the inlet of the pneumatic conveyor at regular intervals does not necessarily and invariably entail the arrival of such articles at the receiver at regular intervals. In many instances, the articles which are confined in the pneumatic conveyor accumulate into groups of closely adjacent articles. Consequently, the quantity of rod-shaped articles in the magazine of the receiver is likely to fluctuate within an excessive range, even if the sender is operated to intermittently admit articles at identical intervals. On the other hand, it is evidently desirable and advantageous to ensure that the receiver invariably contain a requisite quantity of rod-shaped articles so as to account for eventual fluctuations of the frequency at which the sender admits articles into the pneumatic conveyor, for eventual interruptions of operation of the sender, as well as for fluctuations in the rate at which the filter tipping machine or another processing machine consumes the articles which are transferred thereto from the magazine of the receiver.
Attempts to eliminate the aforediscussed problems in connection with the operation of heretofore known senders and receivers include the proposal to admit into the pneumatic conveyor predetermined quantities of rod-shaped articles per unit of time, namely quantities at least slightly exceeding the maximum anticipated quantities which are to be withdrawn from the magazine of the receiver, as long as the quantity of rod-shaped articles in the magazine is less than a prescribed minimum quantity, i.e., as long as the overall number of articles in the magazine is below a preselected threshold value. The quantity of articles in the magazine of the receiver is monitored by a detector which transmits a signal as soon as the level of the stored supply has reached a preselected maximum acceptable value or has descended below a minimum acceptable value. Signals which are generated by the detector are used to actuate a control unit which serves to regulate the operation of the sender, namely to select the number of articles which are propelled per unit of time in such a way that the sending of articles is interrupted when the supply of articles in the magazine has reached the aforementioned maximum permissible level, and that the transmission of articles is resumed when the level of the supply of stored articles has descended below the aforementioned minimum acceptable value.
German Auslegeschrift No. 1 900 149 discloses a proposal to avoid intermittent stoppage of the sender by equipping the apparatus with a blocking or arresting device which is responsive to signals from the monitoring means and serves to reduce the quantity of propelled articles per unit of time when the quantity of articles in the magazine of the receiver has risen to a preselected maximum value, and to increase the quantity of propelled articles per unit of time when the supply of articles in the magazine is depleted to a preselected minimum acceptable value. In other words, the blocking device can regulate the quantity of articles which reach the sender per unit of time in dependency on the extent to which the magazine of the receiver is filled with articles.
The proposal in the Auslegeschrift fails to address and/or solve the problems which arise as a result of the accumulation of propelled articles into groups before such articles reach the outlet of the pneumatic conveyor. The accumulation of articles into such groups entails their deceleration in the pneumatic conveyor and can lead to partial or complete clogging of the conveyor. The possibility of such clogging imposes limits upon the maximum permissible length of the pneumatic conveyor which, in presently known apparatus, is not in excess of 300 meters.